A centralized control network such as OpenFlow described in Non-Patent Literatures 1 and 2 is known. It is known that, when load is concentrated on a control apparatus (controller) in the centralized control network, setting necessary control information (flow entries) would be delayed, which makes communications to be unable to be performed, otherwise, traffics to be blocked will keep flowing in the control apparatus.
Patent Literature 1 discloses a configuration that decreases the load on the controller, by decreasing the number of inquiries of flow entries (a “Packet-In message” described in Non-Patent Literature 2), where the inquiries of the flow entries are causes of increases in the load on the controller. Specifically, a switch described in Patent Literature 2 stacks packets that have caused the controller to inquire the flow entries, then, the switch controls to forward a packet that includes same header information as that of the stacked packets until the flow entries are set. In this process, if being configured to cause a broadcast to be performed for the packet including same header information as that of the stacked packets, it is possible to realize a communication until the flow entries are set.
Patent Literature 2 discloses a configuration comprising, when an existing flow entry is changed to another flow entry that generates an inquiry of the existing flow entry, predicting load on the controller caused by this change, then, dividing (subdividing) the existing flow entry when the load exceeds an allowable value.
Patent Literature 3 discloses a configuration comprising embedding processing contents into a packet, wherein the processing contents are applied to the packet, in order to decrease a number of inquiries of the flow entries.    Patent Literature 1    International Publication No. WO2013/051386 A1    Patent Literature 2    International Publication No. WO2011/083682 A1    Patent Literature 3    International Publication No. WO2011/115168 A1    Non-Patent Literature 1    Nick McKeown, and seven others, “OpenFlow: Enabling Innovation in Campus Networks”, [online], [searched on Apr. 7, 2014], Internet <URL: http://archive.openflow.org/documents/openflow-wp-latest.pdf>    Non-Patent Literature 2    “OpenFlow Switch Specification” Version 1.1.0 Implemented (Wire Protocol 0x02), [online], [searched on Apr. 7, 2014], Internet <URL:http://archive.openflow.org/documents/openflow-spec-v1.1.0.pdf>